Terminal for electric cables.



0'. W. DAVIS. TERMINAL FOR ELECTRIC GABLES.

urmcurox FILED mm: 5, 1907. 9,830, Patented Apr. 27, 1909.

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5 L 6 jgvslfrron @MM 6 6 CHARLES W. DAVIS, OF EDGEWORTH, PENNSYLVANIA.

TERMINAL FOR ELECTRIC CABLES.

Specification of Letters Patent.

Patented April 2'7, 1909.

Application filed June 5, 1907. Serial No. 377,435.

To all whom it may concern:

Be it known that l, CHARLES IV. DAVIS, residing at lfldgeworth, in thecounty of Billegheny and State of Pennsylvania, a citizen of the UnitedStates, have invented or discovered certain new and useful Improvementsin Terminals for Electric Cables, of which improvement the following isa speciiication.

My invention relates to improvements in preventing the ingress ofmoisture within the cable sheath, and to guard against leak age, wherethe sheath is interrupted, as at a terminal, where a lead-sheathedunderground cable is joined to an aerial line or lines.

Cables of ordinary construction contain insulating material ofhygroscopic character, and in such case any moisture which gets accessto the interior tends to destroy the insulation and to permit leakage.

In the accompanying drawings, which form part of this specification,Figure 1 shows in vertical section a terminal for a cable embodying myimprovement. Figs. 2 and 3, Show a Structure similar to that of Fig. 1,but 'ith modifications in detail which form parts of my presentinvention.

In Fig. 1 I have shown my plug construction combined with other parts toform a complete terminal. In this construction, the plug 2 consistsessentially of a central core of conducting material, and of asurrounding petticoated insulating body. This central core may be asingle integral piece, as shown and described in application Serial No.309,197, filed March 31, 1907, but is preferably formed of two parts 1and 1 the part I being of annular form and having the insulating body 2formed upon it, and screw-threaded within to' receive the part 1*, whichis correspondingly threaded. Thus the part 1 may be separated from andmoved relatively to the part 1 and the insulating body 2, for thepurposes presently to be described. The part 2, that is the surroundingbody of insulating material formed as described, has a screw thread 5formed upon its outer surface for the purpose of attachm nt to the otherparts, which together with it form the terminal structure. This screwthreaded surface extends above the plane of the lower edge of thepetticoat at, and thus the joint is effectively protected against theweather. This terminal, illustrated in Fig. 1, is peculiarly applicableto a cable consisting of a single conducting core, l employ as a case orshell the thimble 6 which is substantially cylindrical in form. it oneend the thimble is of suitable size to slip over the lead-sheathed cableT and to be attached thereto by the wiped soldered joint 10. At theother end this thimble is connected to the plug, preferably in suchmanner, that the point of connection will be protected by the petticoat.These parts, namely the plug with its removable piece 1 and the thimble(3 are constructed in the factory ready for field use. The manner ofapplying them will be readily understood.

By making the core of the plug in two parts, connection with the cableconductor can be made readily, by what is known as a sweated joint,which in such constructions is ordinarily far preferable. The end of thecable, which in this instance is a cable having a single conductor, isfirst stripped of its lead sheath and of the layer of insulatingmaterial, and the conducting core 8" is itself laid bare. To this baredend of the conductor the central portion 1 of the plug is electricallyconnected by the familiar sweated joint. Vhen the part 1 is thusconnected, the thimble 6 is slipped down over the end of the cable andthe part 1 with the petticoat insulating body molded upon it, is thenslipped over the part 1 and screwed down to position. The thimble 6 isthen attached to the plug and its opposite end secured by suitablemeans, as a wiped joint to the sheath of the cable.

In case the material of which the insulating body 2 is formed, is ofsuch character that said body would be injru'iously affected by heatconveyed to it through the junction box or thimble at the time offorming the wiped solder joint, in consequence of the relatively highconductivity of the material used to form such thimble, I may resort toeither of two expedients. I may, in assembling the parts, use a guideprovided with screw threads corresponding in size and position with thescrew threads of parts 1 and 2 and first apply such guide in place ofthe insulating body to the core 1 and assemble the thimble and make thewiped joint, and then remove the guide and apply the parts 1 and 2 inplace of it. In Such case the threads whereby the cone is connected tothe conductor andthe insulating plug to the thimble, should be similarin pitch and direction. This construction also the easy filli of thethimble with in sulating material. Or, I may form the thimble itselfwholly or in part of a material of relatively low heat conductivity.

The diiliculty in this connection is due to the fact that such metals asare of suilicient hardness to retain a screw thread tapped upon them,are ordinarily of high thermal conductivity; and it will be found bestunder practical conditions, to form the upper end f the thimble of sucha metal as brass, in which the screw thread may be formed, and the lowerend of such metal as lead which is of relatively low heat conductivity.This is indicated in Fig. 1. On the other hand, it may be preferred toform the thimble entirely of lead in the following manner. When the bodyof insulating material 2 (see Fig. 3) is formed, it may be molded withina lead tube which will afterward be shaped to form the thimble by I thenthe contacting surfaces would tend to dressing in the free end of thelead tube to the shape indicated in the drawings. In this case therewill be no screwing together of parts 2 and 6"; but these parts will beunited when applied, and they will be applied as one piece over the part1 and the cable end after the sweated joint has been formed. Whenapplied and seated the wiped solder joint 10 will be formed. The innersurface of the tube upon which the insulating body is molded willpreferably be corrugated, as shown in Fig. 3. In following thisalternative last described, the lead of whici the tube is formed willpreferably be hardened by the addition of a small proportion of tin.

It will be observed that if desired, the interior space within thethimble 6", may be filled with some fluid or viscid insulating material,and it will be further observed that by suitably constructingand'arranging the parts, the upper end of the thimble 6 may he made toabut against the body of insulating material within the protection ofthe petticoat a. Here a gasket 15 may be introduced to further securethe joint against ingress of moisture. It will be understood that theaerial line may be con nected with the projecting end 1 of the terminalstructure in any desired or preferred manner. It will be understood thatthe position of this terminal when com pleted should preferably besubstantially that shown with the petticoat a of theplug extendingdownward and protecting by its encircling downwardly extending surface,the conductor arranged in substantially vertical position, so that theleakage from the aerial to the lead sheath of the cable 7 isinterrupted.

The variation shown in Fig. 2 from the structure shown in Fig. 1 liesprimarily in forming a thimble of two pieces 6" and 6 screw threaded soas to be secured together in the manner shown, so that instead ofattachment to the cable sheath by the wiped soldered joint 10 of Fig. 1,connection may be made by means of a stuffing gland 16. in thismodification also the connection between the insulating body 2" and thethi1nble 6", instead of being external in respect to the insulation body2", is internal. In this instance too, is shown means whereby intimatecontact may be maintained between the core of the plug and itssurrounding body of insulating material, although the mate rial of whichthe insulating body is formed, is such that as the insulating substancegrows cooler it expands relatively to the conducting body. If such werethe case in the construction illustrated in Fig. 1 for instance-that isif the substance of which body 2" is formed, expanded relatively to thecentral body 1" as the newly-molded body cooled down to normaltemperature,-

open, and so far as they open the structure would be defective.

In Fig. 2 I have shown the body 1" provided exteriorly with an inwardlyenlarging cavity 17 and the insulating body 2" formed over that surfaceof the part 1", which is provided with this inwardly enlarging cavity17, and thus surfaces of contact between the bodies 1" and 2", areprovided, over which union will grow more intimate as the cooling body2" expands relatively to the body 1".

Fig. 3 illustrates another modification from the form shown in Fig. 1.In this instance the part 1" of the central core is not internal withrespect to the body 2", but it is an annulus in shape, and is made tobear upon the body 2. The annulus 1" may be grooved along its inner edge18, and into this grooved inner edge, the body 2 may be fitted. It willbe observed that in this instance also, relative expansion of thesubstance of body, 2" compared with body 1 will but serve to increasethe closeness of the union ofthe two bodies. As in the other instancethe body 1 may extend through the body 1 and the parts be securedtogether by a screw thread if desired.

in forming a connection between the conductor of a cable and an aerialline, the in sulation must be removed from the conductor of the cablefor a short distance and provision must be made to prevent moisturepenetrating the insulation of the cable. These ends are attained in myimproved construction, wherein a body of insulating material is appliedto the bare conducting surface beyond the insulation of the cable andpreferably closely adjacent to the end of such insulation, and a sleeveor thimble extends from the insulatiir body to the metal sheath, beingsecured to the latter preferably by a wiped joint. The insulating bodyis detachably secured to both the conductor and to the thimble as byscrewthreads. This construction permits of the thimble and insulatingbody to be put together, slipped onto the conductor and when the aerialand conductor have been electrically connected, the insulated bodysecured in position on the conductor, 6., screwed onto the thread dportion tuereof, th reby bringing the thimble into proper position whereit is secured to a sheath by a wipe joint. The insulated body can thenbe unscrewed from the conductor and thimble, the latter filled withinsulating material and the insulating material and the insulating bodyreplaced. 4

.l claim herein as my invention:

1. A terminal structure for an electric. cable consisting of a plug anda case or thimble, said plug consisting of a centrally arranged andvertically disposed conducting core and a surrounding body of insulatingmaterial in moisture tight contact thereon, and formed externally with asurrounding downwardly and outwardly flaring leakage preventingpetticoat, said case or thimble being in leakage proof engagement withtne cable sheath at one end and with the plug at the other end, theengagement of the case or thimble with the plug being arranged withinthe protection of the petticoat.

2. A terminal structure for an electric cable consisting of a plug and ametal case or thimble, said plug consisting of a centrally arranged anda vertically disposed conducting core and a surrounding body ofinsulating material in moisture tight contact thereon, and formedexternally with a surrounding downwardly and outwardly flaring leakagepreventing petticoat, said metal case or thimble being in leakage proofengagement with the cable sheath at one end and within the plug at theother end, the engagement of the case or thimble with the plug beingarranged within the protection of the petticoat.

3. A terminal structure for an electric cable consisting of a plug and acase or thimble, said plug consisting of a centrally arranged and avertically disposed conducting core and a surrounding body of insulating material in moisture-tight contact thereon, and formed externallywith a surrounding downwardly and outwardly flaring leakage preventingpetticoat, and said case or thimble having a leakage proof engagementwith the cable sheath at one end, and the plug at the other end, theengagement of the case or thimble with the plug being arranged withinthe protection of the petticoat, and a gasket between the body of thecase or thimble and the body of the in a terminal structure and incombination with a case or thimble engaging the sheathed cable and plugengaging such case or thimble, such plug consisting of a core formedwith two separable parts, one of said parts having formed upon it and inmoisture-proof engagement therewith, a body of insulating materialprovided externally with a surrounding downwardly extending leakagepreventing petticoat and having external of the insulating body meanswhereby a separable connection may be made with an aerial wire, and theother part of said core adapted to be connected electrically with acable core, the parts of said plug being arranged and constructed to bebrought together and united to the exclusion of moisture from theirpoint of union.

A terminal structure for a metal. sheathed electric cable consisting ofa conducting core adapted to be electrically con nected with theconductor of the cable and with an aerial wire, a body of insulatingmaterial surrounding and making a moisture-proof engagement with saidcore and provided externally with a surrounding downwardly extendingleakage preventing pettincoat, and a thimble having its end formedrespectively of materials of different character, the harder metalengaging the body of insulating material and the metal of the lowerconductivity secured by a wiped joint with the cable sheath.

6. A terminal structure for a metal sheathed electric cable consistingof a body of insulating material surounding and having a moisture-proofconnection with a conducting core and provided with a surroundingdownwardly extending leakage preventing petticoat, a core adapted to beelectrically connected at its ends with the conductor of the cable andwith an aerial wire, and a thimble having one end secured to the metalsheath and the opposite end connected to the insulated body in suchmanner that such connection will be protected by the petticoat.

7. A terminal structure for a metal sheathed electric cable consistingof a core adapted to be electrically connected with the conductor of thecable and with an aerial wire, a body of insulating material surroundingand having moistureproof connection therewith and provided with asurrounding downwardly extending leakage preventing petticoat and ametal thimble having one end secured to the metal sheath and theopposite end connected to the insulated body, the point of connectionwith the insulating body being above a plane coincident with the loweredge of the petticoat and overhung by the latter.

8. A terminal structure for a metal formed of insulating material inmoisture proof contact with the conductor and provid d wlth a petticoat,the other of said parts secured by hermetical joint to the cable sheathand connected with said first named part beneath the protection of thepetticoat thereof.

10. A two part terminal structure for protecting the connection betweena cable core and an aerial line, one of said parts consisting of aconducting element adapted to form the electrical connection between theconductor of the cable and the aerial line, and having insulatingmaterial secured in moisture proof contact thereon and provided with apetticoat, the other of said parts secured by hermetical joint to thecable sheath and connected with said first named part beneath theprotection of the petticoat.

11. A two part terminal for a metal sheathed insulated cable consistingof a metal thimble adapted to be secured at one end to the cable sheath,and a body of insulating material secured to a bare conductor beyond theinsulation of the cable and secured to the thimble, the body ofinsulating material having a sleeve or prolongation adapted when theparts are assembled and applied to form a shield. or screen between thebare conductor and the thimble.

12. A two part terminal for a metal sheathed insulated cable having incon1bination a metallic thimble adapted to be secured at one end to thecable sheath and having its opposite end threaded, a bared conductorhaving screw threads and an annular body of insulating material providedwith screw threads to engage the conductor and the thimble the severalthreads being of like pitch thereby permitting the insulating body to besimultaneously applied to or detached from the conductor and thimble.

In testimony whereof, I have hereunto set my hand.

7 CHARLES W. DAVIS. Witnesses CHAnLEs BARNETT, F. J. TOMASSON.

